Weird error message when a struct literal is used in a condition of an if statement

Code

fn main() {
    let foo = Foo { x: 3 };
    let x = 3;
    let y = if foo == Foo { x } { x } else { 0 };
}

#[derive(Eq, PartialEq)]
struct Foo {
    x: u32,
}

Current output

error: expected one of `.`, `;`, `?`, `else`, or an operator, found `{`
 --> src/main.rs:4:33
  |
4 |     let y = if foo == Foo { x } { x } else { 0 };
  |                                 ^ expected one of `.`, `;`, `?`, `else`, or an operator

error: could not compile `err` (bin "err") due to 1 previous error

Desired output

In some contexts, the compiler knows that a struct literal can be ambiguous and use parenthesis. But in this context, it does not know which curly brace is for the struct literal. There must be at least a help message that a struct literal can be ambiguous.

Rationale and extra context

No response

Other cases

If I slightly modify the code like below, it gives me a much better error message.


fn main() {
    let foo = Foo { x: 3 };
    let x = 3;
    let y = if foo == Foo { x: 3 } { x } else { 0 };
}

#[derive(Eq, PartialEq)]
struct Foo {
    x: u32,
}


error:


error: struct literals are not allowed here
 --> src/main.rs:4:23
  |
4 |     let y = if foo == Foo { x: 3 } { x } else { 0 };
  |                       ^^^^^^^^^^^^
  |
help: surround the struct literal with parentheses
  |
4 |     let y = if foo == (Foo { x: 3 }) { x } else { 0 };
  |                       +            +


It seems like the compiler uses `:` to figure out whether it's a struct literal or not.

Rust Version

rustc 1.90.0 (1159e78c4 2025-09-14)
binary: rustc
commit-hash: 1159e78c4747b02ef996e55082b704c09b970588
commit-date: 2025-09-14
host: x86_64-unknown-linux-gnu
release: 1.90.0
LLVM version: 20.1.8

Anything else?

link to Rust playground